1. Field of the Invention
The present invention relates to a recording head cartridge which integrates an ink-jet recording head and an ink storing unit for storing an ink to be supplied to the recording head.
2. Description of the Related Art
Recording apparatuses ordinarily used in printers or facsimile systems perform recording on the basis of binary recording data indicating whether or not a dot is present on a pixel. When an original image having many different density levels such as a photograph, a print, a painting, or the like is to be reproduced, any difference between the densities of dots forming a recording image becomes conspicuous, and the image exhibits graininess. In particular, in a highlight portion, this tendency is considerable.
For this reason, an ink-jet recording apparatus of a density multi-value recording system using light and deep inks, and capable of converting the densities of dots to be jetted to a recording medium into multi-values is proposed. According to the density multi-value recording system, when binary data expressing a density is merely converted to three-value data, gradation of a recording image, in particular, gradation of a highlight portion is improved, and graininess caused by dots can be eliminated. As a result, image quality of a recording image can be improved.
In an ink-jet recording apparatus, a proposal has been made for solving a problem caused by an arrangement wherein a recording head for discharging an ink, and an ink storing unit (to be simply referred to as an ink tank hereinafter) are separately arranged. More specifically, since an ink tube or the like is used to supply an ink from the ink tank to the recording head, dust or air enters through connecting portions or the like of this tube, and becomes dust or bubbles in an ink, thus posing a problem of impaired stability of ink discharge. In addition, a cumbersome operation is required to connect a supply tube when the ink tank or the recording head is replaced, and it is difficult to prevent the entrance of bubbles into the ink upon tank or head replacement. Thus, in order to prevent these problems, a recording head cartridge which integrates the recording head and the ink tank has been proposed.
The recording head cartridge is also especially attractive in view of the fact that latest recording heads can be mass-produced at low cost by the same processes used in semiconductor device manufacturing processes. More specifically, with this integrated structure, when the supply of ink is exhausted, the old cartridge is replaced with a new recording head cartridge integrated with a recording head, and the old recording head and ink tank can be disposed.
In the density multi-value recording system using the above-mentioned ink-jet recording apparatus, the dot size of the light and deep inks, the pitches of light and deep ink dots, the dye densities of the light and deep inks, and the like are optimized, thereby decreasing the dye density of the light ink as much as possible. The dye density of the deep ink is increased to increase an optical density, and a density jump occurring at an interface between the light and deep inks is prevented while improving gradation.
Recording systems are known which can satisfy the above-mentioned requirements, using a method wherein a dark ink having a higher dye density is jetted first, then the dye density is sequentially lowered, and finally, a light ink having a lowest dye density is jetted. With this method, a high-gradation, high-resolution, and high-quality image free from graininess can be obtained.
However, when full-color recording is performed by the above-mentioned recording head cartridge arrangement, two types of, i.e., light and deep ink cartridges must be prepared for each of cyan (C), magenta (M), yellow (Y), and black (B) inks, and a carriage which carries a total of eight cartridges to perform scanning movement for recording becomes large in size.
Since recording head cartridges for light and deep inks cannot be integrated with each other, when light and deep ink cartridges of the same color are simultaneously replaced (one ink is rarely used alone), this becomes a cumbersome operation.
Since the operation between an orifice array for discharging a light ink and that for discharging a deep ink inevitably becomes large, a long period of time is required after the deep ink is discharged until the light ink is discharged. In order to perform synchronization between recording data sent from a host apparatus or the like and ink discharge during this period of time, the capacity of a buffer memory for temporarily storing these data must be increased, and cost of the entire apparatus is increased.
Since the separation between the orifice arrays is large, when light and deep inks are jetted to overlap each other, the light ink often overlaps the deep ink after the deep ink is absorbed. In this case, graininess caused by deep ink dots appears, and the image quality of the density multi-value recording system is compromised.
Furthermore, as for the separation between the orifice arrays, since the light and deep ink cartridges are not integrated, as described above, the separation therebetween may be changed upon replacement of cartridges, and this change comprises image quality of a recorded image.
When such recording is performed, it is well known to use the light ink used as frequently as is possible in order to obtain a high-gradation, high-resolution image free from graininess. Therefore, when high image quality of the density multi-value recording system and a cartridge structure of a recording head and an ink tank in consideration of operability are realized at the same time, it will be necessary to replace the cartridge for the light ink more frequently than it will be necessary to replace that for the dark ink.
When replacing the light ink cartridge, the deep ink cartridge must also be replaced (the deep ink is rarely used alone), resulting in waste of the cartridge, which still contains ink.
In order to avoid such waste, a cartridge may have a light ink tank having an increased tank volume. With this structure, however, a difference in tank shape causes a difference in the distance between the heads (the distance between the discharge ports) of the light and deep inks, and the capacity of a buffer memory for performing synchronization between a supply timing of recording data and an ink discharge timing must be further increased, thus posing a new problem.
When a volume difference is compensated for by a flexible ink tank, the cartridges cannot be moved with precision upon recording, and this structure impairs an easy handling feature of the cartridge.